Bifunctional Molecular Modification Improving Efficiency and Stability of Inverted Perovskite Solar Cells

Kinds of interfacial engineering technologies are explored in perovskite solar cells (PSCs), which are proved to be benefit for the devices to achieve higher efficiency, less hysteresis, and/or better stability. In this work, in an inverted p-i-n structured PSC, a monolayer of 5-aminovaleric acid (5-AVA) molecules with bifunctional groups is introduced to modify the surface of p-NiMgLiO compact hole transport layer (HTL). This key surface modification is not only improving the resultant perovskite film's quality, but also facilitating efficient charge extraction at the HTL/perovskite interface, which result in improved power conversion efficiency (PCE) from 18.0 to 19.4%. Furthermore, the 5-AVA-modified device can withstand much higher poling bias (>1.8 V) for a longer time than the pristine one, showing little nonsteady state current and excellent consistency of forward and reverse photocurrent-voltage curves after high bias poling. Benefitting from the exceptionally stable interface, the 5-AVA-modified device shows much improved long-term stability, which can maintain over 90% of its initial PCE after 300 h continuous light soaking at maximum power point tracking condition.